Computer vision systems can be utilized to obtain precise dimensional measurements of inspected objects. Such systems may include a computer and a camera and optical system with a stage that is movable to allow the camera to scan the surface of an object that is being inspected. One exemplary prior art system that is commercially available is the QUICK VISION™ series of vision inspection machines and QVPAK™ software available from Mitutoyo America Corporation (MAC), located in Aurora, Ill. This product is able to provide images of an object at various magnifications, and move the stage as necessary to traverse the object surface beyond the limits of any single video image. A single video image typically encompasses only a portion of the object being observed or inspected, given the desired magnification, measurement resolution and physical size limitations of such systems.
Visions systems such as Quick Vision™ are generally designed to facilitate industrial inspection. Such systems frequently include a lens turret with lenses of various magnifications. It is common to inspect various aspects of a single object using the various magnifications. Furthermore, in industrial inspection environments, very large inspection objects are common, and dimensions to be measured often extend beyond a field of view. In such systems, a convenient and ergonomically intuitive manual motion control system that consistently addresses all the above factors is of great utility.
In contrast, in conventional laboratory vision systems which utilize microscopes, a single video image may often encompass an entire object or the object may extend a relatively small distance outside the filed of view, given the generally small size of objects observed by such systems. Some systems include a manual motion control system that responds to manual input, and the response to the input is linearly scaled according to a selected magnification. The joysticks in certain other systems include a contact switch which triggers high speed motion at large deflections.
An example of a vision system utilizing a microscope that includes dual joystick control modes for inspection and manipulation of relatively small objects is shown in U.S. Pat. No. 5,677,709. The system of the '709 patent teaches a joystick which controls a micromanipulator which is used to three dimensionally position an object in the field of the microscope. The system can be operated in a speed control mode and a position control mode. In the speed control mode an actuator is driven by a speed corresponding to the inclined amount of the manipulating lever for the joystick. In the position control mode, the actuator is driven by a distance corresponding to the inclined amount of the manipulating lever of the joystick. The system switches between the speed control mode and the position control mode according to a change-over switch. One of the problems that the '709 patent addresses is that when the mode is switched from the position control mode to the speed control mode while the joystick is inclined, the system will be started in motion even if this was not the intent of the operator. The '709 system avoids this problem by only switching between the modes when the joystick is in the neutral position. While the method of the '709 patent addresses certain issues regarding switching between modes in a joystick controlled microscope vision system, it still requires switching between the two modes in an inconvenient manner. In addition, none of the above systems offer a robust and appropriate method for manually controlling the motion axis of a machine vision system that alters the focus of the system.
The present invention is directed to providing a method that overcomes the foregoing and other disadvantages. More specifically, the present invention is directed to a method for converting the deflection of joystick or other manual control device into motion which uses speed/deflection profiles that are selected in accordance with the present lens characteristics of the system.